Prosthetic or orthopedic interfaces typically interact with a patient's body, and may be in direct contact with the skin. These interfaces can cause irritation and pain if not interfaced properly with the wearer's skin. Rigid devices such as neck and back braces or casts can create pressure sores and chaffing, while less rigid devices, such as bandages and wraps, may suffer from poor breathability or cause skin irritation.
Numerous liners or paddings are employed in prosthetic and orthopedic systems, and serve as an interface between a corresponding device and the body of the wearer. For example, in prosthetic devices, a suspension liner is generally understood as a sleeve worn over a post-operative stump or limb that serves as the interface between the limb and prosthesis or a prosthetic device, such as a hard socket. These liners are typically made of an air impermeable elastomer material, such as silicone. The liners may comprise a single layer or multiple layers, with different layers providing different benefits to the wearer. Examples include U.S. Pat. No. 4,923,474 granted May 8, 1990, U.S. Pat. No. 6,706,364, granted Mar. 16, 2004, and U.S. Pat. No. 9,050,201, granted Jun. 9, 2015, each incorporated herein by reference.
Liners are used traditionally to provide cushioning to a residual limb by distributing pressure on the limb caused by a prosthetic device. The liner also protects the limb from irritation that might be caused by movement of the prosthesis against the limb. Absent a liner, the prosthesis will directly contact the skin. Any movement or slippage of the prosthesis at the interface with the limb will therefore result in friction between the prosthesis and limb and, irritation to the limb. Presence of the liner between the limb and the prosthesis eliminates this problem by serving as a protective barrier between the limb and the prosthesis; movement at the interface with the limb will be borne by the liner and not the limb.
Some users find known liners to be uncomfortable for several reasons, including poor pressure distribution resulting from the limb-liner-socket interface. When using a prosthetic socket, normal and shear forces are generated upon the skin of the residual limb. Many known liners fail to distribute pressure evenly about the residual limb, causing areas of the limb to be subject to pressure greater than others. The concentrated pressure areas can cause discomfort, pain, and pressure marks.
In another form, the interface may be used interchangeably with a spacer element, as taught and discussed in U.S. Pat. No. 8,425,441, granted Apr. 23, 2013, and incorporated herein by reference. According to this embodiment, a spacer element or liner is a compressive pad along a frame for an orthopedic device, thereby serving as an interface between a rigid or semi-rigid frame and the limb of the user.
Another interface feature that provides comfort is breathability. Many known interfaces are made of materials that do not breathe or wick moisture away from the residual limb when donned. Without a breathable interface, moisture and heat buildup on the surface of the skin. Excess moisture may create foul odors, and cause chaffing and irritation. The raised surface temperature of the skin increases the temperature of the interface and changes its material properties.
Users also find many known interfaces difficult to don and doff. Liners may be found too thick or inflexible, making them hard to don and doff because they are inflexible or there is too much friction between the skin and the liner.